Recently, in common communication systems, satellite communication systems, and television systems, demands for high-frequency high-power transistors have increased. Generally, in order to provide high-frequency transistors which can provide high output power, a structure including a plurality of transistor cells in a single transistor chip or in a transistor package is used. A transistor with such a structure, however, will have small input and output impedances, which makes it difficult to provide good impedance matching with respect to external circuits. When such a transistor is connected to external circuits with poor impedance matching, undesirable power loss is caused at input and output sections of the transistor, which degrades operating efficiency. Accordingly, such situations must be avoided.
A technique to avoid the above-stated problem in high-frequency high-power transistors is to provide an MOS capacitor, for example, in a transistor package. An LC circuit includes the capacitance provided by the MOS capacitor and the inductance provided by bonding wires connected to input and output electrodes of the transistor. The LC circuit constitutes an internal matching circuit to provide impedance conversion for proper impedance matching with external circuits.
Further analysis, however, has shown that because bonding wires connecting an output electrode, e.g. collector electrode, of each transistor to various portions of that transistor (i.e. a portion closer to the MOS capacitor, a portion remote from the capacitor, and an intermediate portion between them) act differently, operating characteristics of those portions are non-uniform and, accordingly, improvements in efficiency or output power of the transistor are not achieved as desired.
Accordingly, an object of the present invention is to provide an improved high-frequency high-power transistor having an internal matching circuit therein.
Specifically, an object of the present invention is to provide an internal matching circuit which acts uniformly on various portions contributing to the transistor function on a transistor chip, so that the operating efficiency of the transistor is increased to thereby provide high output power.
Another object of the present invention is to make as uniform as possible the effects of the inductance of the bonding wires of an internal matching circuit, and characteristics of various portions contributing to the transistor functions on a transistor chip, whereby the operating characteristics of the respective transistor portions become uniform and the output efficiency of the transistor is improved.
Still another object of the present invention is to make as uniform as possible the lengths of the bonding wires of the output side internal matching circuit with respect to the various portions exhibiting transistor functions on the transistor chip so that the operating characteristics of the respective transistor portions become uniform to improve the output efficiency of the transistor.